Additive manufacturing techniques are well known.
An example of additive manufacturing is 3D printing, in which an object is formed layer by layer. Additive manufacturing may be contrasted with conventional machining techniques in which material is removed by, for example milling and drilling.
The different kinds of additive manufacturing have method specific advantages and disadvantages. Factors to be considered are speed of manufacture, strength of material, accuracy of manufacture and limitations of shape and form inherent in the manufacturing process.
One method of additive manufacturing forms a solid component from liquid base material contained in a bath. The liquid is caused to solidify, generally in successive layers, until the finished component can be lifted from the bath. The excess liquid is drained for re-use, and the component is washed and dried. One feature of this method is that the component has uniform characteristics, which are defined by the base material. This may be very advantageous in some circumstances, but it would also be desirable to be able to vary some characteristics as the part is being manufactured. By way of example, variation of colour and/or material strength would significantly enhance the usefulness of components produced by this technique.
Whilst it may be possible to change the base liquid during manufacture, to achieve an outer layer of material with a different characteristic, this step may be slow and in any event the range of different compatible materials may be small.
Further, no satisfactory method of additive manufacturing cross-linked or actively cross-linking polymers, such as silicone elastomer components, has hitherto been devised, particularly at room temperature. Such components would be beneficial in numerous applications in which the stability, inertness, resilience, strength and/or temperature resistance of such materials are required.
What is required is an improved method and apparatus for additive manufacturing, in particular in-bath manufacturing, that can provide a variation of material characteristics within a component produced by these means and/or produce a polymer such as a silicone elastomer component that is suitably strong, resilient and dimensionally stable in a relatively rapid process.